JP6117223B2 - Treated inorganic core particles with improved dispersibility - Google Patents

Description

  The present disclosure relates to a method of producing treated inorganic core particles, typically titanium dioxide particles, and in particular, to producing treated inorganic oxide core particles with improved dispersibility, typically titanium dioxide particles.

Titanium dioxide particles such as pigments and nanoparticles are produced using either the chlorination method or the sulfidation method. In the production of titanium dioxide pigment by the gas phase chlorination method, titanium tetrachloride, TiCl ₄ is treated with an oxygen-containing gas at a temperature of about 900 ° C. to about 1600 ° C., and a high-temperature gas obtained from TiO ₂ particles and free chlorine. The suspension must be cooled immediately, eg, below about 600 ° C., by discharging it from the reactor and passing through a tube or air line. Therefore, the titanium dioxide pigment particles are grown and aggregated.

  In order to improve the hiding power and durability of the final product, it is known to add various substances such as silicon compounds and aluminum compounds to the reactants. Aluminum trichloride added during the process has been found to increase rutile in the final product, and silicon tetrachloride, which becomes silica in the final product, is carbon black undertone (CBU), particle size and It has been found to improve pigment wear. However, in addition treatments and processes additionally used for these treatments, the treated titanium dioxide particles have poor dispersibility.

  Efficiency of adding inorganic core particles, typically metal oxide particles produced by pyrolysis, more specifically titanium dioxide particles to form treated inorganic core particles with improved dispersibility Is needed.

In a first aspect, the present disclosure provides:
(A) A slurry comprising porous silica-treated inorganic core particles and water is at a temperature of at least about 90 ° C, more typically from about 93 to about 97 ° C, and more typically from about 95 to about 97 ° C. Heating with
(B) While maintaining the pH at about 8.0-9.5, a soluble alumina source is added to the slurry from step (a) to form an alumina treated product on the porous silica treated inorganic core particles. And wherein the treated inorganic core particles are free of high density silica or alumina treatment, and are present in an amount of at least about 7% to about 14% and from about 4.0% to about 8%. Treated inorganic core particles with improved dispersibility, in particular treated titanium dioxide (TiO ₂ ), having alumina present in an amount of 0.0% and the surface treatment being substantially homogeneous from particle to particle A method of manufacturing the same is provided.

In a first aspect, the present disclosure provides a method in which treated inorganic core particles, particularly treated titanium dioxide (TiO ₂ ) particles, are fully dispersed in water to form a slurry in less than 10 minutes.

  “Homogeneous” means that each core particle is added to the surface of a certain amount of alumina and silica so that all particles interact in the same way as water, organic solvent or dispersant molecules, so that the level of processing between the particles varies. (Ie, all particles interact with their chemical environment in a common way to a common range).

  “Completely dispersed” refers to the reduction of the total aggregates formed during the water treatment and / or drying process into individual particles or small populations (aggregates) of particles made during the particle formation stage of pigment production. Means that

In the first aspect, as described below, the silica is co-oxygenated with silicon tetrachloride and titanium tetrachloride by deposition onto the exothermic inorganic core particles of exothermic silica, in particular exothermic titanium dioxide (TiO ₂ ) particles. Or by deposition by condensed phase aqueous oxide precipitation onto inorganic core particles, particularly exothermic titanium dioxide (TiO ₂ ) particles.

In a first aspect, the present disclosure provides a slurry comprising silica treated inorganic core particles, particularly treated titanium dioxide (TiO ₂ ) particles and water.
(A1) providing an underwater slurry of inorganic core particles;
(A2) heating the slurry to about 30 to about 40 ° C., more typically 33 to 37 ° C., and adjusting the pH to about 3.5 to about 7.5;
(A3) adding a soluble silicate solution to the slurry while maintaining the pH at about 3.5 to about 7.5;
(A4) providing a method of preparation by a process comprising stirring for at least about 5 minutes.

  In this disclosure, “comprising” is to be construed as specifying the presence of a specified feature, integer, step or referenced component, but of one or more features, integers, steps or components or groups thereof. It does not exclude existence or addition. Furthermore, the term “comprising” is intended to include examples encompassed by the terms “consisting essentially of” and “consisting of”. Similarly, the term “consisting essentially of” is intended to include examples encompassed by the term “consisting of”.

  In this disclosure, when an amount, concentration or other value or parameter is given as either a range, a typical range or a list of typical upper and lower limits, the ranges are individually disclosed. Whether or not, it is considered to specifically disclose all ranges made from any upper or typical value and any pair of any lower or typical value. Unless otherwise specified, the numerical ranges shown here include their end points and all integers and fractions within the ranges. The scope of the disclosure is not limited to the particular values indicated when defining a range.

In the present disclosure, the terms “a”, “an”, and “the” in the singular and singular forms also include the plural unless specifically stated otherwise. Thus, for example, “TiO ₂ particles”, “theTiO ₂ ”, or “aTiO ₂ ” include single and plural particles.

  The present disclosure relates to inorganic core particles, typically inorganic metal oxide or mixed metal oxide pigment particles, and more typically titanium dioxide particles, which can be pigments or nanoparticles, Have improved dispersibility of inorganic metal oxide or mixed metal oxide particles, more typically titanium dioxide particles.

Inorganic core particles:
Any inorganic core particles, in particular titanium dioxide particles, shall be treated according to the present disclosure. Inorganic core particles mean those that are dispersed throughout the final product, such as a polymer melt, coating or laminate composition, to impart color and opacity. The inorganic core particles are titanium, aluminum, zinc, copper, iron oxide; calcium, strontium, barium sulfate; zinc sulfide; copper sulfide, zeolite; mica; talc; kaolin, mullite, calcium carbonate or silica. Good. Lead or mercury compounds are also considered equivalent core materials, but are undesirable due to toxicity. More typical core materials are titanium dioxide TiO ₂ and barium sulfate, most typically titanium dioxide TiO ₂ .

In particular, titanium dioxide is a particularly useful particle for the methods and products of the present disclosure. Titanium dioxide (TiO ₂ ) particles useful in the present disclosure are in the rutile or anatase crystal form. Generally, it is produced by either a chlorination method or a sulfuric acid method. In the chlorination method, TiCl ₄ is oxidized to TiO ₂ particles. In the sulfuric acid method, sulfuric acid and ore-containing titanium are dissolved, and the resulting solution is passed through a series of steps to obtain TiO ₂ . Both sulfuric acid and chlorination methods are described in detail in “The Pigment Handbook”, Volume 1, Second Edition, John Wiley & Sons, NY (1988), the teachings of which are incorporated herein by reference. The particles may be pigments or nanoparticles.

  “Pigment” means titanium dioxide particles having an average size of less than 1 micron. Typically, the average particle size is from about 0.020 to about 0.95 microns, more typically from about 0.050 to about 0.75 microns, and most typically from about 0.075 to about 0.50 microns. “Nanoparticle” means that the primary titanium dioxide particles have an average particle size of less than about 100 nanometers (nm) as determined by dynamic light scattering to measure the particle size distribution of the particles in a liquid suspension. Means. The particles are typically aggregates that can range from about 3 nm to about 6000 nm.

Process for producing treated titanium dioxide particles The process for producing treated inorganic core particles with improved dispersibility, particularly treated titanium dioxide (TiO ₂ ) particles, comprises a slurry comprising porous silica treated inorganic core particles and water. Heating at a temperature of at least about 90 ° C, more typically about 93 to about 97 ° C, and more typically about 95 to about 97 ° C. Silica is produced by deposition of exothermic silica on exothermic inorganic core particles, in particular on exothermic titanium dioxide (TiO ₂ ) particles, by co-oxygenation of silicon tetrachloride with titanium tetrachloride, or by deposition of condensed phase aqueous oxides. Applied by

In one embodiment, a silica-treated inorganic core particle, particularly a slurry comprising treated titanium dioxide (TiO ₂ ) particles and water, is prepared by a method comprising providing an underwater slurry of inorganic core particles. Typically, TiO _2, based on the total weight of the slurry, 25 to about 35 wt%, and more typically present in an amount of about 30 wt%. The slurry is then heated to about 30 to about 40 ° C., more typically 33 to 37 ° C., and the pH is about 3.5 to about 7.5, more typically about 5.0. Adjust to ~ 6.5. A soluble silicate such as sodium silicate or potassium is added to the slurry while maintaining the pH at about 3.5 to about 7.5, more typically from about 5.0 to about 6.5. Thereafter, stirring is performed for at least about 5 minutes, typically at least about 10 minutes, but not more than 15 minutes, to facilitate precipitation into inorganic core particles, particularly titanium dioxide (TiO ₂ ) particles. SiO ₂ / Na ₂ O weight ratio of from about 1.6 to about 3.75, solid in 32-54% by weight, is most practical commercial water soluble sodium silicates may or may not be further diluted . To apply porous silica to inorganic core particles, the slurry is typically acidic during the addition of an effective amount of soluble silicate. The acid used has a dissociation constant sufficient to precipitate the silica and is used in an amount sufficient to maintain acidic conditions in the slurry, such as HCl, H ₂ SO ₄ , HNO ₃ or H ₃ PO ₄ Any acid may be used. A compound such as TiOSO ₄ or TiCl ₄ that hydrolyzes to form an acid may be used. Instead of adding all of the acid first, soluble silicate and acid may be added simultaneously as long as the acidity of the slurry is typically maintained at a pH of less than about 7.5. After the acid addition, the slurry must be kept at a temperature below 50 ° C. for at least 30 minutes before proceeding with further addition.

  The treatment corresponds to about 7 to about 14 wt%, more typically about 9.5 to about 12.0% silica, based on the total weight of the inorganic core particles, particularly the titanium dioxide core particles. Controlling the isoelectric point between 5.0 and 7.0 can be advantageous in promoting dispersion and / or aggregation of the particulate composition in factory processing and end use.

An alternative method of adding the treated silica to the TiO ₂ particles is as described in US Pat. No. 5,992,120, which is incorporated by reference, with exothermic silica, particularly exothermic inorganic core particles, Of silicon tetrachloride by deposition on pyrogenic titanium dioxide (TiO ₂ ) particles or as described in US Pat. No. 5,562,764 and US Pat. No. 7,029,648. By co-oxygenation with titanium chloride.

  The slurry comprising the porous silica treated inorganic core particles and water is heated at a temperature of at least about 90 ° C, more typically from about 93 to about 97 ° C, and more typically from about 95 to about 97 ° C. . The second treated product contains precipitated aluminum oxide or alumina. This treatment is porous and is typically applied from a soluble alumina source, such as a soluble aluminate, using techniques known to those skilled in the art. In certain embodiments, a soluble alumina source, such as a soluble aluminate, is used while maintaining a pH of about 7.0 to 10.0, more typically 8.5 to about 9.5. It is added to a slurry containing treated titanium dioxide to form a treated alumina on the porous silica-treated inorganic core particles. The “soluble alumina source” means, for example, an alkali metal salt of an aluminate anion such as sodium aluminate or potassium. Alternatively, the soluble alumina source may be acidic, for example, aluminum chloride. In this case, the pH is controlled using a base rather than an acid. The treated inorganic core particles do not include a high-density treated product of silica or alumina.

  The treated porous alumina is about 4.0% to about 8.0%, more typically about 5.0% to about 7.%, based on the total weight of the inorganic core particles, particularly the titanium dioxide core particles. Present in an amount of 5%. Since substantially all of the precipitated alumina is treated with inorganic core particles, typically that amount of a soluble alumina source, such as a soluble aluminate, will have an appropriate degree of treatment after precipitation. As such, it only needs to be applied to the slurry liquid.

Typically, the particle-by-particle surface treatment is substantially homogeneous. This is because the treatment level at the alumina and silica levels between the particles so that each core particle attaches to the surface of an amount of alumina and silica so that all particles interact in the same way as water, organic solvent or dispersant molecules. (Ie, all particles interact with their chemical environment to a common extent in a common way). Typically, the treated inorganic core particles, particularly the treated titanium dioxide (TiO ₂ ) particles, are fully dispersed in water to form a slurry in less than 10 minutes, more typically less than about 5 minutes. . “Completely dispersed” means that the dispersion is made up of individual particles or a small population of particles (hard aggregates) made in the particle formation stage, and all soft aggregates have been reduced to individual particles Means that.

  After treatment by this process, the pigment is recovered by known procedures including neutralization of the slurry, if necessary, filtration, washing, drying, and often dry grinding steps such as miniaturization. However, since a high viscosity slurry of the product can be used directly to make an emulsion paint in which water is in the liquid phase, drying is not necessary. This process is an easy and efficient way to obtain a highly solid water slurry of fully dispersed particles.

Although the present disclosure is not bound by theory of operation, the improved dispersibility of the porous treated TiO ₂ pigments of the present disclosure is believed to be due to the nature of the treatment and its application.

Use Treated inorganic core particles, typically inorganic or mixed metal oxide particles, more typically titanium dioxide, coating compositions such as paints, plastic parts such as molded articles or films, or It may be used for paper lamination. The paper laminate of the present disclosure is useful for flooring, furniture, countertops, artificial wood surfaces and artificial stone surfaces.

  The following examples illustrate the present disclosure. All parts, percentages and ratios are by weight unless otherwise indicated.

Example 1
The TiO ₂ oxidation bases 2000 g, was slurried in deionized water 4520Ml, to a concentration of 400gTiO ₂ / liter (30.7wt% TiO _2). The slurry was heated to 35 ° C. and the pH was adjusted to 5.5. Sufficient HCl was added to sodium silicate solution (1210 grams) to maintain the pH between 4-6. After curing for 5 minutes (with mixing), the slurry was heated to 55 ° C. Sufficient HCl was added to 695 grams of sodium aluminate to maintain the pH at 6. While maintaining the pH and temperature, the slurry was stirred for an additional 30 minutes before being filtered, washed, dried and vaporized. The resulting sample has a percent SiO ₂ value of 14% and a percent alumina value of 7.6%.

Example 2
The procedure described in Example 1 was used except as described below.
• After 5 minutes of silica curing, the slurry was heated to 95 ° C.
• During and after aluminate addition, the slurry pH was maintained at 9.0 and the temperature at 95 ° C.

Sample Evaluation slurry prepared easiness: in latex paint manufacturing, generally, it is desirable to prepare high solids water slurry of TiO ₂ pigment that can be incorporated other mixed slurry containing other paint ingredients. Typically, this TiO ₂ pigment slurry is made in a separate dispersion step with equipment specially designed to disperse the submicron particles (eg, Hockmeyer disperser, Katy mill or Dispermat disperser). For sample evaluation, a slurry of each pigment example was made with a Hockmeyer disperser with the following amounts of components.
• 3000 g TiO ₂ pigment • 1953 g water • 0.9 g TKPP (potassium tripolyphosphate) dispersant • 0.5 g Proxel® (biocide)

A slurry was made by incrementally adding TiO ₂ pigment to a mixing pot containing all of water, TKPP and Proxel® while shearing at 1,000 rpm. Dispersibility (easy to disperse) was quantified for the time required for the total mass of pigment to be fully incorporated into the slurry. For Example 2, this time was less than 1 minute. The sample of Example 1 was not fully incorporated into the slurry under a shear condition of 2,000 rpm, although an additional 9 grams of dispersant (TKPP) was added to the slurry. Thus, the advantages of the disclosed sample are obvious.

Color strength: Color strength is a measure of the scattering ability of a white pigment. White pigments are added to paints, plastics or paper laminates and scatter visible light, so high tinting strength is desirable. In this test, a standard white pigment of the relevant TiO _2, using a polymer binder (trade name AC-347), was prepared by TiO ₂ content 26% PVC.

  Diluted green dye (GW-951P) was made by mixing 1 part dye with 2 parts deionized water. Green dye was added to the white paint at a level of 3 grams of dye per 100 grams of paint. At this level, the Y value measured for dry paint was close to 50%.

Each paint was drawn down with a uniform white card using a 0.004 inch gap blade and allowed to air dry. After drying, a second coat of the same paint was applied to a portion of the card with a brush and the resulting paint was vigorously brushed to create a “brush out” portion of the panel. The Y color value is determined three times for each drawdown, separately for both the drawdown area and the brushout area as it is. Drawdown was also performed using a paint made of standard TiO ₂ for the purpose of comparing the sample with known pigments.

K / S value
K / S = [(1-Y) ² ] / [2 ^* Y]
To calculate for each drawdown region using the tristimulus Y values. The tinting strength value is recorded as the ratio of the K / S value of the standard paint divided by the K / S value for the paint made with the pigment of interest and is recorded as a percentage. Shear strength uniformity, which is a measure of pigment dispersion stability when the paint dries, was determined by comparing the K / S value in the area where the drawdown was left as it was and the K / S value in the brushout area.

  The drawdown color strength, brush-out color strength and shear uniformity of Example 1 were defined as 100. The drawdown tinting strength, brush-out tinting strength and shear strength uniformity of Example 2 were measured as 103, 104 and 101. The fact that the value for Example 2 was greater than Example 1 indicates that Example 2 provided higher tinting strength and is desirable for white pigments.

Weighted hiding power (propagation speed): Weighted hiding power (propagation speed) is a measure of the ability of a white pigment to cover the surface appearance of a substrate. This was determined using the contrast ratio and was based on the theory of dependent light scattering. The paint was made with a different TiO ₂ pigment as described in the description of the tinting strength test, except that no colorant was added (ie, the paint was white). The shear rate was measured for these paints by a series of steps. First, the exact blade gap was determined by drawing down the paint with black and white cards using several different blades with a gap between 0.0025 and 0.0035 mils. These drawdown contrast ratios were determined by the ratio of the light reflected by the black area of the panel (tristimulus Y) divided by the Y value measured in the white area of the panel. The drawdown blade was selected so that the contrast ratio was 92-95.

  The four charts were then drawn down into black and white cards for each paint and control paint of interest. The drawdown weight was measured immediately and the total amount of paint applied was determined therefrom. The painted card was allowed to air dry overnight. Thereafter, an average Y value was calculated from four values measured from each part (black or white) of the card.

  The contrast ratio of the paint was determined by dividing the reflectance value measured at the black portion of the card by the reflectance value measured at the white portion of the card. The contrast ratio and reflectivity for the black value are entered into a computer program using the Kubelka-Munk equation, and a perfect hiding power (complete hiding is defined as when the contrast ratio exceeds 0.98). Estimated square feet covered by gallon paint. This square foot was called the “propagation velocity” of the pigment. A high propagation speed is preferable because it indicates a high hiding power. The propagation speed of Example 1 was determined to be 308.4 square feet per gallon and the propagation speed of Example 2 was determined to be 337.0 square feet per gallon, increasing the diffusion efficiency by approximately 10%.

Claims (8)

(A) forming a slurry containing silica-treated inorganic core particles and water;
(B) heating the slurry containing the silica-treated inorganic core particles and water at a temperature of at least 90 ° C .;
(C) While maintaining the pH at 8.0-9.5, a soluble alumina source is added to the slurry from step (b) to form an alumina treated product on the silica treated inorganic core particles. A process for producing a coating composition comprising the steps of:
The step (a)
(A1) providing an underwater slurry of inorganic core particles;
(A2) heating the underwater slurry from (a1) to 30-40 ° C. and adjusting the pH to 3.5-7.5;
(A3) adding a soluble silicate solution to the underwater slurry from (a2) while maintaining the pH at 3.5-7.5;
(A4) stirring the underwater slurry from (a3) for at least 5 minutes;
The treated inorganic core particles from step (c) are silica present in an amount of at least 7 wt% to 14 wt% and 4.0 wt% to 8.0 wt%, based on the total weight of the inorganic core particles. % Alumina present in an amount of
A manufacturing method in which a surface treatment product is substantially homogeneous between particles.   The inorganic core particles are titanium, aluminum, zinc, copper or iron oxide, calcium, strontium or barium sulfate, zinc sulfide, copper sulfide, zeolite, mica, talc, kaolin, mullite, calcium carbonate or silica. The method of claim 1. The method according to claim ₂ , wherein the inorganic core particles are titanium dioxide, TiO ₂ or barium sulfate. The method according to claim 3, wherein the inorganic core particles are titanium dioxide and TiO ₂ . The method of claim 1 wherein the slurry of step (b) is heated to a temperature of 93 ~ 97 ° C.. The slurry of step (b) A method according to claim 5 which is heated to a temperature of 95 ~ 97 ° C..   The method of claim 1, wherein the soluble alumina source is an alkali metal salt of an aluminate anion.   The method according to claim 7, wherein the soluble alumina source is sodium aluminate or potassium aluminate.